Means for regulating electric steam generators



Jan. 2, 1940.

M. EATON 2,185,786

MEANS FOR REGULATING ELECTRIC STEAM GENERATORS 4 Sheets-Sheet 1 FiledNov. 28, 1 938 Jan. 2, 1940. M. EATON 2,185,786

MEANS FOR REGULATING ELECTRIC STEAM GENERATORS Filed Nov. 28, 1938 4Sheets-Shet 2 Jan. 2, 1940. M, E T N 2,185,786

MEANS FOR REGULATING ELECTRIC STEAM GENERATORS Filed Nov. 28, 1938 4Sheets-Sheet 5 51 wag-T] F us a us F F n4 m 5 l04a t o c 106a n o c Pg85 4 M. EATON 2,185,786

MEANS FOR REGULATING ELECTRIC STEAM GENERATORS Filed Nov. 28, 1938 4Sheets-Sheet 4 Patented Jan. 2, 1940 um'rso STATES PATENT OFFICE MEANSFOR REGULATING ELECTRIC STEAM GENERATORS Milton Eaton, Shawinigan Falls,Quebec, Cauada, assignor to Shawinigan Chemicals Limited, Montreal,Quebec, Canada, a corporation Application November 2a, 1938, Serial No.242,827 In Canada November 8, 1938 24 Claims. (01. 219-40) It is aprincipal object of the invention to provide a system for automaticallyregulating the rate of evaporation, that is the power input,

in boilers of this type in response to deviations in a condition ofoperation, which it is desired to maintain constant and whichwill thusbe referred to as the selected condition. This selected condition, ofwhich the power input to the boiler m is, according to the invention, adetermining factor, may be, alternatively, a constant adjustable boilerpressure, a constant adjustable power input, or a constant total powerdemand as will become evident from the detailed description to follow.

It is a further object of the invention to provide in combination withthis system, means for limiting the current that can be taken at anyboiler water level, independently of the selected condition. 4

With these and other objects in view, the present system is featuredbynovel regulating means for adJustlng the power input (1. e., rate ofevaporation) in response to variations in the selected condition (ordeviations from the control point of the selected condition), throughautomatic step by step variation of the water level on. the boilerelectrodes. Electrical controlling means is provided, having a timedholding circuit for timing the operation of the regulating means toaccomplish the step by step variation.

Daawmcs Other aspects of the invention will become 45 evident from thefollowing description of one of its preferred embodiments shown in theaccompanying drawings, in which:

Figure l is a diagram illustrating the arrangement of special mechanicalapparatus associated 50 with a three-electrode boiler in which theelectrodes are each connected to a phase of a power supply.

Figure 2 is a cross section along the line 2-2 of Figure 1. a Figure 3is a wiring diagram illustrating an electrical system for controllingthe apparatus shown in Figure 1.

Figure 4 is a schematic wiring dimer!!- of the system illustrated inFigure 8.

Figure 5 is a fragmentary schematic diagram 5 similar. to Figure 4,illustrating the use of an alternative formof timing means for thecontrol circuits.

Figure 6 is a diagrammatic view of the timing device used in connectionwith the system of Fig- 10 ure 5. Drrmm Dsscsrr'rron The boilerReferring more specifically to the drawings, 18 A represents the shellof an electric boiler of established design. Within the shell A andinsulated therefrom by insulators 60 are three electrodes l2, and meansof conducting electric current into the electrodes, including conductorsI3. 20 H is an inlet pipe for feed water, It is a bleed connection, andit a steam outlet. An internal shell H, connected with the outer shellA, constitutes a grounded neutral to the electrodes. Water is shown inthe boiler A partially immers- 2s ing the electrodes l2.

The boiler is supplied with water from the feed water line it through amain regulating valve 15a. controlled by a float mechanism ll. The valveIlla is operated by float ill (in float chamso ber 3i) communicatingwith an elevated control tank B and interconnected leverarms I32 andI33, actuated'in a manner to be described, so as to maintain the waterlevel in the boiler and control tank, under ordinary conditions,approxia5 mately at a constant level. A bypass IT is provided to bypassthe regulating valve I50 and is controlled by a manually operable valvei8. A valve l8a is positioned in the feed water line it between thebypass l1 and the valve I50. 0

Fundamental boiler operation In operation of the boiler, the electriccurrent, passing through the water surrounding the electrodes l2,generates heat energy which is dissipated in raising steam. The neutralshell H obtains substantially uniform current density on the surface ofthe electrodes and avoids electrolytic corrosion oi the outer shell.

In a boiler of this type, the applied voltage is constant and the powerinput, 1. e., rate of evaporation, is regulated by varying the current,the latter being governed by the resistance of its path through thewater. This resistance depends on three factors, namely, (1) thespecific resistance and temperature of the boiler water, (2) the crosssectional area of the path of the current through it, and (8) its meanlength. The

speciflc resistance is determined by the concentration of salts insolution. The cross sectional area of the path of the current varieswith the water level on the electrodes. The electrode spacing (thedistance between one another and neutral shell) determines the distancethe current must travel through the water. Thus, the power input isdirectly proportional to the electrode area immersed, and to the saltconcentration in the water. The salt concentration tends to increase dueto salts carried into the boiler by the feed water and is held withinsatisfactory limits by continuous or intermittent bleeding. As boilerwater is bled off, it is replaced with comparatively pure feed water andhence the salt concentration in the water becomes diluted.

The power input may be controlled in three ways, namely, (a) by varyingthe water level on the electrodes with the salt concentration maintainedsubstantially constant, (b) by using a salt solution to vary the saltconcentration, with the water level maintained substantially constant,or (c) by a combination of these two methods.

The present system According to the present invention, the power input,and hence the selected condition of which it is a factor, areautomatically regulated by varying the water level on the electrodes(according to (a) previous paragraph) with the aid of a regulating andcontrol system to be described in detail. The salt concentration is heldwithin predetermined limits by automatically regulating the bleeding offof boiler water by means of elements forming a part of this system whenthe load current at any water level becomes greater than normal for thatlevel. Through the arrangement of the system referred to, variation ofthe water level on the electrodes is made responsive to the controlledcondition, whereas the limitation of the salt concentration isindependent of it.

This system ofl'ers advantages, as compared with those disclosed in theprior art. For instance, it is not limited in its application either bythe choice of condition desired to be regulated, or by boiler loadconditions such as degree of fluctuation in steam demand, and feed waterconductivity. In fact, there is no other automatic control equipmentavailable for application to the type of boiler referred to, which willvary the boiler load over its full range and in such a manner as tomaintain constant total power demand, i. e., boiler power plus motorpower, held constant. A further advantage is obtained in the use of stepby step correction with intervening pauses to allow time for response.This tends to avoid hunting and provides for stability.

Rnetms'non V The eontrol'tank and boiler Having dealt generally with theprinciples underlying the present invention by reference to aconventional boiler, more detailed attention will now be given to theregulating system mentioned. In this system, as an adjunct to boilerwater level regulation, a water column I9 is associated with the boilershell II and a series of pipes 20, 20a, 20b and 200, connects differentlevels of the column I! with corresponding positions spaced along acylinder 2|. A pipe 22 connects the cylinder 2i at a point directlyopposite the connection of pipe 20, corresponding with the lowest aromaswater level, with the top of an elevated control tank 3. The connectionsto the water column correspond with the highest and lowest practicablewater levels on the electrodes and equally spaced intermediate levels,the spacing of the pipes 20, 204, etc., and hence their number, beingarbitrary. The use of six levels has been found satisfactory. A piston24 operates in the cylinder to connect or shut oil. the pipe 22progressively from the pipes 20, 20a, 20b, etc., so that various levelsin the boiler may be connected to the top of the control tank. A pipe 25connects the bottom of the control tank to the bottom of the boiler,this pipe being controlled by a valve 26. An outlet 21 is provided tothe pipe 25 and is controlled by a valve 23. The bottom of the controltank is connected to the feed water line l4 through a pipe 2!!controlled by a valve 30.

The float mechanism 3|, connected with the 'control tank at midelevation, controls the feed water regulator valve lia, increasing ordecreasing its opening as the water level in the tank falls or risesrespectively. Alternatively, a thermostatic type of regulator, such as aCopes feedwater regulator, might be used if desired, instead of thefloat type.

, The control tank is also provided with a bleed connection 32controlled by a needle valve 33. The steam on entering the control tankis condensed and consequently entrained permanent gases tend toaccumulate. Excessive accumulation is avoided by a light continuousbleed through needle valve 33. The gases are mixed with the steam, henceboth steam and gases are bled oil. The concentration of gases is limitedby the rate of bleed which need not be greater than 1 cubic foot in 10to 15 minutes, depending on the proportion of gases in the steam andrate of condensation, e. g., assuming the proportion of gases in thesteam to be parts per million and rate of condensation 10 cubic feet perminute a bleed of 1 cubic foot in 15 minutes limits the concentration toone half of one per cent (0.5%) which would not be objectionable.

This control tank and boiler arrangement and its function as describedare believed to constitute a new development in the art.

Water level selecting apparatus,

For actuating the piston 24 there is'provided, adjacent the cylinder 2|and in axial alignment therewith, another cylinder 40 in which ismounted a piston 4|. The pistons 24 and 4| are inter-connected by apiston rod 42 extending through the ends of the respective cylinders.Diiferent ends of the cylinder 40 are connected through suitable pipeswith three-way solenoid operated valves 43 and 44, the circles 2 and ldenoting connections with the control system, to be described later,from the solenoids of these valves. These valves are connected with thefeed water supply pipe l4 or any other suitable source of hydraulicpressure through a throttling valve 45. The valve port openings are suchthat hydraulic pressure is normally applied to both ends of the cylinder40. If, however, the valve 44 is energized, pressure to thecorresponding end of the cylinder 40 is cut oil and the water in thatend is released through a third port in the valve. This causes thepistons 4| and 24 to move to the right. Similarly, if the valve 43 isenergized, these pistons move to the left. The piston speed is adjustedby means of the throttling valve 45. The valves 43 and 44 are controlledby the elec- 7 by a solenoid operated valve 52.

aiasgrso trical control system by which it is controlled.

Alternatively, the valve 52 may be motor operated.

Feed water regulation For a better understanding of the function of theapparatus already described, before the details of the electricalcontrol system are dealt with, reference will now be made to feed waterregulation under normal conditions while the selected condition remainsunchanged.

When steam is permitted to rise in the conduit 22, e. g., when theposition of the piston 24, is to the right of one or more of theconduits 20, 20a, etc., above the boiler water level-water flows fromthe control tank to the boiler by gravity through pipe 25, the rate .01flow depending upon the pipe resistance. It access of steam to conduit22 is cut off, e. g., by the piston 24 being to the left of all theconduits 20, 20a, etc., above the water level, the direction of flow inthe conduit 25 reverses, the rate of flow depending upon the rate ofcondensation in the control tank. Steam is used in supplying radiationlosses and in raising the temperature of water taken from the bottom ofthe boiler. If the resulting rate of condensation is not fast enough, itmay be increased by admitting relatively cool feed water directly to thecontrol tank through the valve 30, the rate depending upon thethrottling adjustment of this valve.

In this arrangement, access of steam to conduit 22 and the control tankI9 depends on the position of the piston 24 in the cylinder 2| inconjunction with the water level in the boiler. As shown in the diagramof Figure 1, if the boiler water level rises any higher, access of steamto conduit 22 is cut of! and, as condensation in the control tank Bproceeds, pressure in it is maintained by transfer of water from theboiler through pipe 25. As the water level in the tank rises, the floatmechanism 3| reduces the opening of the valve i5a, thus decreasing therate of feed water flow to the boiler through pipe l4. When the boilerwater level has fallen below the conduit 20b, steam is again admittedtothe control tank through the pipes 20b and 22; gravity flow to theboiler through pipe 25 is thus resumed. As the control tank water levelfalls, the opening of the feed water regulator valve l5a is increased,thus accelerating the feed water flow through pipe I.4.- The boilerwater level again rises and the above cycle is repeated. In this manner,although the feed water passes directly to the boiler through the pipeI4, its rate of flow is directly dependent upon the water level in thecontrol tank B, which in turn depends upon conditions within the boileritself.

It is essential that the feedwater regulator should function to keep thecontrol tank half full; there is then water stored for raising the levelin the boiler and space for transfer of water to drop the level in theboiler.

Selection of water level When it is desired to increase the power inputof the boiler, as for. instance to return the selected condition tonormal, the piston.24 is moved to the right, permitting access of steamfrom pipes of the series 20, 20a, etc., at higher water levels on thewater column, causing adjustment or the water, through the regulatingapparatus 5 described, to a higher level. Similarly, ii it is desired todecrease the power input, the piston 24 is moved to the left and thewater in the boiler subsequently adjusts itself to a; lower level. The

selection of a water level in this manner is be- 10 lieved to be novel.

Connor.

Governing instrument The control system, as will eventually be describedin greater detail, controls the movements of the piston 24 and,consequently, is instrumental in causing the changes in the boiler powerinput. This system is setin operation, to vary the boiler water level,by a governing instrument 10. Since this instrument responds tovariations in the selected condition, its nature depends upon thecondition selected. For instance, it this conditionis one of constantadjustable boiler pressure, the instrument is a pressure actuated de- 25vice connected mechanically with the boiler. II it is desired tomaintain constant adjustable power input the governing instrument is amanual device, used to adjust the boiler water level to correspond withthe desired power input.

When it is required that the control should function to maintainconstant power input to the boiler, governing instrument 10 is a manualpushbutton station used to adjust the-boiler water level to correspondwith the desired load. Instru- 35 mentalities associated with thecontrol system then function, as described later, to maintain the loadcurrent, or power input, corresponding with the water level. Theseinstrumentalities may be adjusted to maintain any predetermined loadcorresponding with" a fixed water level, within the limits ofpermissible current density.

Alternatively, it may be desired to maintain constant total powerdemand, 1. e,, boiler power plus motor and other power, possibly equalto 45 the maximum demand on which the contract with the power company isbased. In this case the control instrument 10 will be a contactmakingwattmeter located in the circuit supplying the boiler power and allother power, such 50 as that required for motors, lighting, etc. Thiswill cause the boiler power to be increased or decreased as the motorand other power falls and rises.

A principal advantage of the present system is 55 that it is not limitedin its application either by the selected condition desired to beregulated, or by boiler load conditions. It should be noted, however,that when the control equipment is used to maintain either constantpower input to the o0 boiler, or constant total power demand, the steampressure must be governed by a coal fired boiler or boilers, operatedwith the electric boiler, or by other suitable means. The coal firedboiler or boilers supply the excess of steam demand over 68 thatsupplied by the electric boiler, hence the"; coal boiler must regulatethe steam pressure.

The piston-travel limit switch distance, for instance, the distancebetween a pair of the pipes 20a, 2011, etc. For this purpose there isprovided in conjunction with the control g system, to which it isconnected through a connection indicated by the circle 4, a limit switchD operable'by the piston rod 42. One side of the limit switch Dcomprises alternate segments 52 and 53 (Figure 3) of conducting materialinsulated from one another, the segments 52 being connected to aconductor 84 leading to the control system. At the other side of thelimit switch is a conducting rod or bar 05 connected to a conductor 86also leading to the control system. This switch also includes a contactarm 5| contacting the segments 82 and 03 and the conducting rod 05, thiscontact arm being operatively connected to the centre part of the pistonrod 42. The distance between the insulated non-in terconnected segments03 of the limit switch, referred to as "stop segments", is the same asthe spacing of the pipes 20, 200, etc., connected with the cylinder 2|.In addition, the piston 24 and the contact arm 8| have a space relation,such that when the contact arm engages a stop segment 02, the piston 24is midway between two adjacent pipe connections 20, 20a, etc. Theoperation of this limit switch will be described in conjunction withthat of the control system.

The tap selector switch To limit the amount of current that can be takenat any boiler water level, independently of the selected condition,there is provided for operation in conjunction with the control system atap selector switch E, also actuable from the piston rod 42. The twosides of the switch E are similar to those of the limit switch D,adjacent segments of one side being connected to solenoid taps on anovercurrent relay. The switch E includes a contact arm 80 contacting thesegments and contact bar of the switch in such a manner that when thecontact arm of the limit switch is moved from one stop segment to thenext in either direction by the piston rod 42, the contact arm 80 of thetap selector switch moves from the centre of one segment to the centreof an adjacent one. Through connections illustrated by the circle 5, thetap selector switch E, is connected to the control circuit and to thetransformer 81, as best illustrated in Figure 3. The manner of operationof this switch will also be described later in conjunction with thecontrol system.

Electrical control circuits As illiwtrated diagrammatically in Figure 3,and schematically in Figures 4 and 5, the electrical control systemincludes a circuit having conductors IN and I02 connectable to asuitable power -supply source through a switch S. For utilizing thiscircuit to operate the valves 44, 43 and 52, the conductor MI isconnected directly to one terminal of the solenoid of each of thesevalves, while the other conductor I02 is connectable respectively to theother terminal of each of these solenoids through a suitable magneticswitch or relay, as will be described in detail. In Figure 3, theconnections between the elements of the control system and the solenoidsof the valves which they control are indicated by the circles I, 2 and3, which thus correspond to the similar circles in Figure 1.

Motor driven timers According to one embodiment of the invention thereis associated with the control system a timing device F including amotor H5 driving two cams H3 and H4 in a clockwise direction. As the.cam H4 rotates it momentarily'opens, in each revolution, a pair ofcontacts H8. The

synchronism but are normally at rest in their relative positions shown.

A similar apparatus G includes a motor H driving a cam I00, in eachrevolution oi which a pair of contacts II I are momentarily opened and apair of contacts H2 are momentarily closed. The motor and cam rotatecontinuously.

Control relays The relays referred to include a pair of relays I03 andI04 operating as one to control the valve 44, another pair of relays I05and I05 operating as one to control the valve 43, a relay I00controlling the bleed valve 52, and an overcurrent relay I0l. The relaysI03, I04 and I05 include respective, normally open, pairs of contactsI03a-IOIc, I04a-I 04cetc., and normally closed pairs of contacts I03b,I04b, and N51). Relay I06 includes three normally open pairs of contactsI05a, I06b, and I050. Relay I08 has two pairs of normally open contactsI08a, and Mic. The contacts of the overcurrent relay I01 are normallyopen.

Control circuit connections The control circuit connections are bestillustrated in the schematic diagram, Fig. 4. A switch 8 is used toconnect conductors IN and I02 with a suitable source of control powersupply. One terminal of the solenoids of all relays, and valves, and oneterminal of each motor is connected directly with conductor II, with theexception of the solenoid of relay I01. The other terminals of theseelectrically operated devices are connectable with the other side of thecontrol circuit, conductor I02, through the operation of relay contacts,limit switches, etc.

The solenoid of relay I05 is connected with contact 12 of governinginstrument I0, through contacts I03b, also with one contact of the pairI050, the other contact of which is connected with conductor I02 throughcontacts H0 of timing device F. The solenoid of relay I03 is similarlyconnected through contacts I05b with contact 'H of the governinginstrument, and through contacts I030 with contact H8.

Contacts I031: and I05b thus serve as electrical interlocks making itimpossible for relays I03 and I05 to be energized at thesame time.Contacts I030, I050, and H8 of timer F, together with connections,constitute timed holding circuits, the function of which will bedescribed later.

The circuit maker 13 of governing instrument I0 is connected directly toconductor I02.

The solenoids of relays I04 and I06 are connected with one contact ofthe pairs [03a and I05a respectively. The other contacts of these pairsare connected with conductor I 02.

The motor H5 of the timer F is connectable with conductor I02 throughthe operation of contacts I04c, I05c, or contacts H5 of the timer F.

The solenoids of valves 44 and 43 are connected with one contact of thepairs I04a and i080 respectively. The other contacts of these pairs areconnected together and with one contact of the pair Ill of timer F, alsowith conductor 84 leading to the interconnected segments of limit switchD. Element 85 of the limit switch and the other contact of the timercontacts 1, are connected with conductor I02.

The solenoid of relay I08 has three parallel circuits making itconnectable with conductor I02. One leads through contacts I08b of relayI08, another through contacts I04b and the contacts of relay I01. Thethird circuit through contacts I080 and contacts III of timer G, is aholding circuit.

One solenoid terminal of overcurrent relay I'I is connected withoneterminal 01 current transformer 81 located in one of the powerconnections to the boiler. Other solenoid taps I, 2, 3, and 4 areconnected with tap selector switch E. Contact element 93 of the tapselector switch is connected with the other current transformerterminal. The normally open contacts II2 of the timer G are connectedacross the terminals of the current transformer.

Motor IIO, driving cam I09 of timer G, is connected directlyv betweenconductors IN and I02 so as to be continuously operated.

The solenoid of bleed valve 52 is connectable with conductor I02 throughthe contacts I 08a.

OPERATION Control of selected condition Having thus described the natureof the electrical control system, reference will now be made to itsoperation in controlling the regulating apparatus. For example, if theselected condition falls below normal, contact is made between circuitmaker I3 and the contact II in the governing instrument I0 energizingthe relay I03. This in turn, energizes relay I04 and the solenoid of thethree-way valve 44, causing it to operate and the pistons M and 24 inthe hydraulic mechanism to move to the right. When the relay I03 closes,its pair of contacts I030 complete a holding circuit, holding the relayclosed. Contacts I04c of relay I04 also close thus energizing motor I I5of timer F causing cams II4 and II 3 to rotate. At the same time,contacts I041) open to stop or prevent independent operation of bleedvalve 52 by opening the circuit between the solenoid of relay I08 andcontacts of relay I0'I.

The contact between the contacts II'I of the timer F is held long enoughto carry the contact arm 8| of the limit switch D from a stop segment 83to the adjacent inter-connected segment 82. This maintains the circuitthrough the limit switch as contact is broken through the timer contactsII'I until the limit switch contact arm reaches the next stop segment83, which breaks the circuit, causing the valve 44 to becomede-energized and the pistons M and 24 to stop in their new positions.

This piston movement, as has been described, causes the boiler water torise to the next higher fixed level. If the resulting increase in powerinput does not return the selected condition to normal, this operationis' repeated on the next closure of contacts H1 in the timer F and theboiler water is carried still higher. When contact in instrument I0 isbroken, the next momentary opening between contacts I I8 of timer- Fbreaks the holding circuit to relay I03 causing relays I03 and I04 todrop out. Contacts I04a open to preclude operation of valve 44 and thetimer motor is stopped on the next opening of contacts IIB.

If, on the other hand, the selected condition rises above normal,contact is made between the :ircuit maker I3 and the contact I2 of thegoverning instrument l0, energizing relays I05, I06

and the solenoid of the valve 43. This causes the pistons 4| and 24 tomove to the left. A similar operation to that described in the previousparagraph causes the boiler water level to be lowered in successivesteps until the power input is reduced sufiiciently to break contact inthe governing instrument I0.

The operation of the timer and-the limit switch causes the pistons and24 to move directly from one stop position to the next without arcing atthe regulating instrument contacts or consequent chattering of therelays. The timer cam speed must be such that the boiler water has timeto assume that level corresponding with any piston stop position beforethe pistons are permitted to move to the next. Also, the piston speed,as determined by the throttling adjustment'of the valve 45, should be asfast as possible without causing over-travel.

When the relay I06 is energized, its contacts I061) close to energizethe relay I08, which in turn energizes the solenoid of the valve 52causing the latter to open. The relay I08 is held in on a holdingcircuit through contacts I080 and contacts III of timer G. This causesthe relay I08 to remain energized and the bleed valve to stay open aslong as the selected condition is high, and contact is held between thecircuit maker I3 and contact 12 of the goveming instrument I0.Bleedingassists in reducing the boiler power input and also permits theminimum possible power input to be taken at the lowest water level. Therate of bleeding, which should not be greater than necessary, asdetermined by experience, depends on the throttling adjustment of thevalve 5|. When contact is broken between contacts I06b the nextmomentary opening between the contacts II I, causes relay I08 to dropout and the bleed valve to close.

If optimum water level is in between two fixed levels, it hunts betweenthem, but, since the bleed valve 52 operates each time the water levelis lowered, the higher fixed level is held after two or three cycles, 1.e., bleeding reduces the salt concentration in the boiler water, andhence the water level must be raised to maintain the same power input.

Control circuits using alternative timing device The schematic diagrams,Fig. 5, illustrates the use of an alternative type of timing device Hwhich may replace the device F, and has a different arrangement ofcontacts and includes two interconnected relays I30 and I40. The relayI30 has a normally open pairof contacts, I30a, replacing the contactsH8, in the holding circuit for relays I03 and I05. The relay I40 has anormally open pair of contacts, I40a, connected in series with circuitmaker I3 of regulating instrument I0, also a normally open pairof'contacts I40b replacing contacts II'I, Fig. 3.

The timing device H, Fig. 5, as best illustrated in Figure 6 has twocircuit making cams I20 and I2I, driven by a motor I22 through asuitable speed reducing unit. The cams are mounted on a common shaft I23 and made to turn through a maximum angle of something less than 360".When the motor and solenoid I32 are de-energized a spring I24immediately returns the cams to the starting position. Contacts I25 andI26 are normally closed by the cams I20 and I2I. When motor I22 andsolenoid I32 are energized the cams begin to rotate, causing contactsI28 to open almost instantly and contacts I25 to open after cam I20 hasturned through a predetermined adjustable angular distance. This angularadjustment ofcam I20 determines the time period of the device.

In operation, when switch S is closed, relays I30 and I 40 becomeenergized and contacts I30a, HM and I40b close. Now, if the selectedcondition falls below normal, contact is made between circuit maker !3,of instrument I0, and contact II energizing relay I08. Contacts I030'close to form a holding circuit through contacts I30a. Contacts I00aclose to energize relay I04. Contacts I04a close operating valve 44 andcausing the boiler water level to rise. Contacts |04c close energizingmotor I 22 oi timer H thus causing cams I20 and I2I to rotate.- After abrief time interval contacts I25 open thus de-energizing relay I 40 andopening contacts 011 and H011.

This time interval is long enough for contact arm BI of limit switch Dto move to an interconnected segment 02, thus maintaining valve 44energized until pistons H and 24 in the hydraulic mechanism, Fig. 1,move to the position corresponding with the next higher water level atwhich contact arm 0| reaches the next stop segment and valve 44 isde-energized. With contacts I40a open relay I03 is held in by theholding circuit through contacts I03c and I30a.

When the time period of timer H has elapsed, i. e., when contacts I25open, relay I00 is deenergized. Contacts I000 open to de-energize relaysI03 and I04. The timer motor I22 is deenergized allowing cams I20 andI2I to return to their starting position.

If the rise in water level has not corrected the selected condition,contact will still be maintained in the regulating instrument,consequently, when the timer resets, relays I40 and I20 are againenergized closing contacts I30a, H011 and H01) and the above cycle ofoperation is repeated. The water level rises in steps until thecontrolled condition is normal.

If the controlled condition rises above normal a similar operationcauses the water level to fall in successive timed steps until it iscorrected.

The advantage of using the timing device H as compared with the timer F,Figs. 3 and 4, is that the former, with modifications, is, at thepresent time, standard equipment for other applications and available onthe market. The timer used in Fig. 3. would require an adjustable speedmotor and would have to be specially built for this particularapplication. These considerations make the scheme, illustrated in Fig.5, preferable, under certain conditions, but, under other conditions,the control circuits, Fig. 4, might be preferable on account ofrequiring fewer relays.

Control of load current corresponding with boiler water level If theboiler load current exceeds, by a predetermined amount, thatcorresponding with the rated capacity at any water level, the contactsof the relay I01 are caused to close by the current from the currenttransformer 81 in one of the conductors I3. This operation ispredetermined by choice of the ratio of the current transformer and thenumber of turns between taps on the solenoid of relay I01. In Figure 1,the connection between the transformer and the tap selector switch andthe control circuit is indicated by the circle 6.

Since the pull of a solenoid is a function of the solenoid currentmultiplied by the number of turns in the coil or ampere-turns, theboiler load current required to cause operat on. 15 I depends on thecurrent transformer ratio and the solenoid taps with which it isconnected.

As an example it may be assumed that the rated full load boiler currentis 1000 amperes, that the current transformer ratio is 300:1 and that ontap I relay I01 operates with a current of 1 ampere, on tap 2 a currentof 2 amperes causes it to operate, etc. At the lowest operating waterlevel on the electrodes, 1. e., when piston 24 is to the left of pipe20a, the tap selector switch contact arm engages the segment connectedwith relay solenoid tap I and hence a current transformer current of 1ampere causes relay operation. This corresponds with a load current of300 amperes. Similarly at thenext higher water level a load current of600 amperes causes relay I01 to operate. The load current required tooperate the relay at each water level is respectively 300,. 600, 900 and1200 amperes corresponding with 20% over the rated load for each level.

If six water levels were used the load current, causing relay operation,corresponding with each level would be 200 to 1200 amperes in steps of200 amperes.

Another means of obtaining variable load current actuation ofovercurrent relay is to employ a variable resistance connected acrossthe terminals of the relay solenoid. Resistor taps may be connected withthe tap selector switch and resistance values and connections made suchthat at the lowest water level all of the current from the currenttransformer passes through the relay solenoid, which may be wound for acircuit closing current of 1 ampere. At the next higher water level theshunt resistance is made to parallel the relay solenoid, and is of suchvalue that when the current transformer current is 2 amperes only oneampere passes through the relay solenoid and the remainder through theresistor. At the next higher level the tap selector switch reduces theshunt resistance so that with 3 amperes from the current transformeronly one ampere passes through the relay solenoid, etc. It is obviousthat the same results are obtained as with the use of solenoid taps.

When the relay I01 operates it energizes relay I00 to cause operation ofthe bleed valve 52 and consequent reduction in boiler water saltconcentration and load current.

If relay I0! is made to operate with a definite solenoid current ittends to hold in-ai'ter the current falls considerably below that value.This is avoided by periodic closure of timer G contacts II2 which areshunted across the current transformer during each revolution of the camI00, momentarily short-circuiting the relay solenoid and permitting therelay to reset. If the boiler load current has fallen sufliciently, thenext interruption between the contacts III in the holding circuit causesthe relay I00 to drop out and the bleed valve 52 to reclose. However, ifthe load current is still high, relay I0! picks up again thus causingthe bleed to continue for at leas another holding circuit interruption.

The relay I01 and its associated apparatus thus function to limit thecurrent that can be taken at any boiler water level independently of thecontrolled condition. This avoids excessive current density on theelectrodes and limits the load that can be taken at the highest waterlevel.

Anvsrwraens This invention oil'ers several advantages, as compared withprior art disclosures. In the first arouse place it is not limited inits application either in the choice or condition desired to beregulated, or by boiler load conditions, such as for instance degree offluctuation in steam demand and feed water conductivity. The controlfunctions over the full range of boiler load from the greatest that canbe taken at the highest prac ticable water level on the electrodes, tothe minimum possible at the lowest water level. Moreover, it utilizesthe step-method of correction, which is noted for operating stability.

It will be understood that various modifications may be made in thisinvention without departing from the spirit thereof or the scope of theclaims, and therefore the exact forms shown are to be taken asillustrative only and not in a limiting sense, it being desired thatonly such limitations shall be placed thereon as may be imposed by thestate of the prior art or are set forth in the accompanying claims.

The sub-titles used throughout the specification are merely to simplifyreference thereto and should otherwise be disregarded.

I claim:

1. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank forcontrolling the boiler water level, said control tank having a singlesteam inlet, water communication between the bottom of the control tankand the bottom of the boiler, steam communication between said inlet anda level of the boiler corresponding with a selected operative waterlevel on the boiler electrodes, and a feed water supply for the boilerregulated by the watef level in the control tank. I

2. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank, adjustablefeed means for admitting feed water to the boiler in accordance with thewater level in the control tank, said control tank having a single steaminlet, water communication between the bottom of -the control tank andthe bottom of the boiler,

steam communication betwen said inlet and a level oi the boilercorresponding with the selected operative water level on the boilerelectrodes, and adjustable means for causing condensation of steamwithin the control tank at a predetermined adjustable rate.

3. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank, adjustablefeed means for admitting feed water to the boiler in accordance with thewater level inthe control I tank, said control tank having a singlesteam inlet, water communication between the bottom of the control tankand the bottom of the boiler, steam communicationbetween said inlet anda level of the boiler corresponding with a selected operative waterlevel on the boiler electrodes, adjustable means for causingcondensation of steam within the control tank at a predeterminedadjustable rate, and means for bleeding oil from the control tanknon-condensible gases.

4. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank, a feedwater communication to said boiler, a regulator for said communicationresponsive to a water level in the control tank, feed watercommunication with the control tank, adjustable means for throttlingsaid control tank, feed water communication to adjust the rate ofcondensation of steam within the control tank, water communicationbetween the control tank and the boiler, said control tank having asingle steam inlet, and a steam communication between said inlet and alevel of the boiler corresponding with a selected operative water levelon the boiler electrodes.

5. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank, a feedwater communication to said boiler, a regulator for said communicationresponsive to a water level in the control tank feed water communicationwith the control tank, adjustable means for throttling said control tankvfeed water communication to adjust the rate of condensation of steamwithin the control tank water communication between the control tank andthe boiler, said control tank having a single steam inlet. a steamcommunication between said inlet and a level of the boiler correspondingwith a selected operative water level on the boiler electrodes, andmeans for bleeding of! from the control tank non-condensible gases.

6. In an apparatus for regulating electric steam generators, thecombination of an electric boiler, an elevated control tank forcontrolling the boiler water level, means for admitting steam from theboiler to the control tank only when the boiler water is below aselected operative level, free water communication between the boilerand the control tank, and adjustable feed means for admitting feed waterto the boiler in accordance with the water level in the control tank.

'7. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler: water levelregulated means including a control tank and apparatus associatedtherewith for controlling said supply connection to maintain the waterin the boiler substantially at a constant level; water level adjustingmeans including apparatus for establishing communication from the steamspace of the control tank with one of a series of different levels ofthe boiler corresponding respectively with selected operative waterlevels on the boiler electrodes associated with said water levelregulated means to determine the level at which the boiler water is tobe maintained; electrical control means for controlling the action ofsaid regulating means, said control means including an instrumentresponsive to variations in the selected condition for initiating theaction or said adjusting means, and means associated with said controlmeans and governed by said water level adjusting means to limit thepower that can be taken at any water level.

8. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, a control tank, anadjusting cylinder, a connection between the control tank and one end ofthe cylinder, a series of spaced apart connections from the cylinder toprogressively differ-- ent levels in the boiler, an adjusting pistonadapted to travel within the cylinder to connect or disconnectprogressively the boiler connections from the control tank connection, asecond cylinder having an actuating piston adapted to travel therein, apiston rod linking the two pistons, hydraulic means for operating theactuating piston to move the adjusting piston, electrical meansresponsive to variations in the selected condition for initiating theaction of said hydraulic means, and means associated with the electricalmeans and actuated by said hydraulic means for stopping the action ofsaid hydraulic means for definite time intervals.

9. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, a control tank, anadjusting cylinder, a connection between the control tank and one end ofthe cylinder, a series of spaced apart connections from the cylinder toprogressively different levels in the boiler, an adjusting pistonadapted to travel within the cylinder to connect or disconnectprogressively the boiler connections from the control tank connection, asecond cylinder having an actuating piston adapted to travel therein, apiston rod linking the two pistons, hydraulic means for operating theactuating piston to move the adjusting piston, electrical controllingmeans responsive to variations in the selected condition for initiatingthe action of said hydraulic means, and a limit switch associated withthe controlling means and operated by the actuating piston for stoppingthe action of the hydraulic means independently of the selectedcondition.

10. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, a control tank, anadjusting cylinder, a connection between the control tank and one end ofthe cylinder, a series of spaced apart connections from the cylinder toprogressively different levels in the boiler, an adjusting pistonadapted to travel within the cylinder. to connect or disconnectprogressively the boiler connections from the control tank connection, asecond cylinder having an actuating piston adapted to travel therein, apiston rod linking the two pistons, a hydraulic pressure supply,electrically operated valve means connected to said pressure supply andto the second cylinder for operating the actuating piston, an electricalcontrol system including first magnetic switch means controlling theoperation of said valve means, a governing instrument responsive tovariations in the selected condition and adapted to act on said firstswitch means to initiate operation of one of said valves, secondmagnetic switch means associated with said. first switch means andgoverned by the movements of said pistons to stop the operation of thevalves.

11. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, means foradjusting the water in the boiler to any one of a series of selectedlevels, means associated with said adjusting means but actingindependently thereof to maintain the boiler water substantiallyconstant at one of the selected levels, actuating means for operatingsaid adjusting means, an electric control system and a control powercircuit therefor, said system including relays for controlling saidactuating means, a governing instrument to initiate the action of therelays in response to variations from the selected condition, holdingcircuits for the relays including timed circuit-interrupting means andrelay contacts, and a limit switch for stopping said actuating means.

12. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, a control tank, anadjusting cylinder, a connection between the control tank and one end ofthe cylinder, a series of spaced apart connections from the cylinder toprogressively different levels in the boiler, an adjusting pistonadapted to travel within the cylinder to connect or disconnectprogressively the boiler connections from the control tank connection, asecond cylinder having an actuating piston adapted to travel therein, apiston rod linking the two pistons, a hydraulic pressure supply,electrically operated valve means connected to said pressure supply andto the second cylinder for operating the actuating piston, an electriccontrol system including magnetic switch means controlling the operationof said valve means, a governing instrument responsive to variations inthe selected condition adapted to act on said switch means to initiateoperation of said valve means, limit switch means associated with saidfirst switch means and governed by the movements of said pistons tomaintain and to stop the operation of the valve means.

13. An apparatus for regulating electric steam generators to maintain aselected condition of operation subtantially constant comprising incombination a boiler, water level determining means capable of operatingto cause adjustment of the water in the boiler to one of a series ofpredetermined levels, feed water regulating means causing the water toassume and maintain the level corresponding to the adjustment of saiddetermining means, electric means controlling the operation of saiddetermining means, said electric means including instrumentalitiesresponsive to a change in the selected condition for initiating theoperation of the determining means, and means responsive to theoperation of the determining means to stop the operation thereof for adefinite time interval.

14. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising incombination, an electric boiler, a feed water supply connection to theboiler, water level regulated means for contro ling said supplyconnection to maintain the water in the boiler substantially at aconstant level; hydraulically operable water level adjusting meansassociated with said water level regulated means to determine the levelat which the boiler water is to be maintained; solenoid valve means foroperating said adjusting means, a control circuit, control relaysassociated with the circuit for energizing said valve means, a governinginstrument for energizing the relays in response to a variation in theselected condition, circuit interrupting means adapted to maintain atemporary holding circuit to maintain said relays energized, a limitswitch operable by said adjusting means to maintain another holdingcircuit to energize said valve means until the next water level isreached and then to cause the valve means to become deenergized.

15. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant, comprising incombination, an electric boiler, a feed water supply connection to theboiler, bleed means for the boiler, water level regulated means forcontrolling said supply connection; hydraulically operable water leveladjusting means arranged to influence said water level regulated meansto contribute towards determining the level at which the boiler water ismaintained; electrical control means, said control means including aninstrument responsive to a variation in the selected condition forinitiating the action of said adjusting means and of said bleed valve tolower the boiler water level, said instrument also being responsive toan opposite variation in the selected condition for initiating theaction of said adjusting means alone to raise the water level, and meansindependent of the selected condition for stopping the action of saidadjusting means and said bleed means.

16. An apparatus as claimed in claim 15 including electrically operatedmeans for limiting the amount of power that can be taken at any givenwater level, said electrically operated means includinginstrumentalities associated with the control means and responsive tofluctuations in the power supply to the boiler for causing operation ofsaid bleed means.

17. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, aboiler, a feed water supply connection to the boiler; water levelregulated means for controlling said supply to maintain the water in theboiler substantially at a constant level; water level adjusting meansassociated with said water level regulated means to determine the levelat which the boiler water is to be maintained; electrical control meansfor controlling the action of said regulating means, said control meansincluding an instrument responsive to variations in the selectedcondition for initiating the action of said adjusting means; a bleedvalve, bleed valve control means, a tap selector switch for adjustingthe current required to operate said bleed valve control means, saidselector switch being operable by the movements of said adjusting meansto give a definite actuating current for any selected water level, saidrelay being adapted to close when the current reaches a predeterminedvalue.

18. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising, a

boiler, a power supply to said boiler, a feed water supply connection tothe boiler, a control tank, an adjusting cylinder, a connection betweenthe control tank and one end of the cylinder, a series of spaced apartconnections from the cylinder to progressively different levels in theboiler, an adjusting piston adapted to travel within the cylinder toconnect or disconnect progressively the boiler connections from thecontrol tank connection, a second cylinder having an actuating pistonadapted to travel therein, a piston rod linking the two pistons,hydraulic means for operating the actuating piston to move the adjustingpiston, electrical controlling means responsive to variations in theselected condition for initiating the action of said hydraulic means, alimit switch associated with the controlling means and operated from thepiston rod for stopping the action of the hydraulic means independentlyof the selected condition, a bleed valve, electrically operated bleedvalve controlling means, selector switch operated means and associatedcurrent.

transformer making said bleed valve controlling means responsive topredetermined values of boiler load current, said selector switch beingoperated by the piston rod to vary the actuating current according tothe water level, said bleed valve controlling means being renderedoperable when the boiler current reaches a certain limit correspondingwith the boiler water level.

19. In an apparatus of the type described, the combination of anelectric boiler and instrumentalities for the step by step adjustment ofthe boiler water level at any one of a series of selected levels, motoroperated means for controlling said instrumentalities, electrical meanscontrolling the motor operated means and including magnetic relay meanshaving a plurality of contacts, a governing instrument responsive tochanges in a selected condition, circuit holding means actuated by amotor, a limit switch, a circuit through the governing instrument toenergize the relay means, a holding circuit through contacts of therelay means and the circuit holding means to govern the relay means, acircuit through contacts of the relay means and through the circuitholding means to energize said electrical means, a circuit through thelimit switch to energize said electrical means, and control powerconnections to said circuits.

20. An apparatus for regulating electric steam generators comprising incombination, an electric boiler, instrumentalities for efiecting a stepby step adjustment of the boiler water through a series of fixed levels,means responsive to a change in the selected condition for initiatingthe action of said instrumentalities, means independent oi the selectedcondition for stopping said instrumentalities for a definite period atthe conclusion of each step, and means for maintaining the water levelsubstantially constant at one of the fixed levels while the selectedcondition remains normal.

21. In an apparatus of the type described, an electric boiler andinstrumentalities for bringing about a step by step adjustment of theboiler water level, a governing instrument responsive to changes in aselected condition, relays rendered operable by the governinginstrument, electrically operable regulating valves'for actuating saidinstrumentalities, timed holding circuits for maintaining the operationof the regulating valves, and means responsive to the water level in theboiler for breaking one of said holding circuits to stop the operationof the adjusting valves for a definite time interval.

22. In an apparatus of the type described, an electric boiler andinstrumentalities for bringing about a step by step, adjustment of theboiler water level, a governing instrument responsive to changes in aselected condition, relays rendered operable by the governinginstrument, electrically operable regulating valves for actuating saidinstrumentalities, timed holding circuits for maintaining and precludingthe operation of the reg ulating valves, and means actuable by saidinstrumentalities for breaking the holding circuit to stop the operationof the regulating valves.

23. An apparatus for regulating electric steam generators to maintain aselected condition of operation substantially constant comprising incombination, an electric boiler, a feed water supply connection to theboiler, water level regulating means for controlling said supplyconnection including an elevated control tank, water communicationsbetween the boiler and the control tank, and means for admitting steamto the control tank when the water falls below a selected level to bemaintained; hydraulic water level adjusting means associated with saidwater level regulating means to determine the level at which the boilerwater is to-be maintained; electrical control means, said control meansincluding an instrument responsive to a variation in the selectedcondition for initiating the action of said adjusting means, and meansindependent of the selected condition for stopping the action of saidadjusting means.

24. An apparatus for regulating electric steam generators to maintain aselected condition 01' operation substantially constant comprising, aboiler, a feed water supply connection to the boiler, water levelregulating means for controlling said supply connection including anelevated control tank, water communications between the boiler and thecontrol tank, and means for admamas

